import java.security.PrivateKey;
import java.security.PublicKey;

/***
 * 基于二分搜索树实现的映射
 */
public class BSTMap<K extends Comparable<K>,V>  implements Map<K,V>  {

    private class Node{
        public K key;
        public V value;
        private Node left;
        private Node right;

        public Node(K key,V value){
            this.key = key;
            this.value = value;
            this.left = null;
            this.right = right;
        }
    }


    private Node root;
    private int size;

    public BSTMap(){
        root = null;
        size = 0;
    }

    @Override
    public void add(K key, V value) {
        root = add(root,key,value);
    }

    private Node add(Node node, K key, V value) {
        if(node == null){
            size ++;
            return new Node(key,value);
        }
        if(key.compareTo(node.key) < 0){
            //向左子树添加
            node.left = add(node.left,key,value);
        }else if(key.compareTo(node.key) > 0){
            //向右子树添加
            node.right = add(node.right,key,value);
        }else{
            node.value = value;
        }
        return node;
    }

    //查找key对应的节点
    private Node getNode(Node node,K key){
        if(node == null){
            return null;
        }
        if(key.compareTo(node.key) == 0){
            //找到了
            return node;
        }else if(key.compareTo(node.key) < 0){
            //在左子树中找
            return getNode(node.left,key);
        }else{
            //在右子树中找
            return getNode(node.right,key);
        }
    }

    //返回以node为根的二分搜索树最小节点的方法
    public Node mininum(Node node){
        if(node.left == null){
            return node;
        }else{
            return mininum(node.left);
        }
    }

    //删除以node为根的二分搜索树中的最小节点
    public Node removeMin(Node node){
        if(node.left == null){
            //此节点即为要删除的节点
            Node rightNode = node.right;
            node.right = null;
            size --;
            return rightNode;
        }
        node.left = removeMin(node.left);
        return node;
    }

    @Override
    public V remove(K key) {
        Node node = getNode(root, key);
        if(node != null){
            root = remove(root,key);
            return root.value;
        }
        return null;
    }

    private Node remove(Node node,K key){
        if(node == null){
            return null;
        }
        if(key.compareTo(node.key) < 0){
            //去左子树删除结点
            node.left = remove(node.left,key);
            return node;
        }else if(key.compareTo(node.key) > 0){
            //去右子树删除结点
            node.right = remove(node.right,key);
            return node;
        }else{
            //当前节点即为删除结点
            if(node.left == null){
                Node rightNode = node.right;
                node.right = null;
                size --;
                return rightNode;
            }else if(node.right == null){
               Node leftNode = node.left;
               node.left = null;
               size--;
               return leftNode;
            }else{
                //找到比删除节点大的最小节点作为替代节点
                Node successor = mininum(node.right);
                successor.right = removeMin(node.right);
                successor.left = node.left;
                node.left = node.right = null;
                return successor;
            }
        }
    }

    @Override
    public boolean contains(K key) {
        return getNode(root,key) != null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(root,key);
        return node == null ? null : node.value;
    }

    @Override
    public void set(K key, V value) {
        Node node = getNode(root,key);
        if(node == null){
            throw new IllegalArgumentException(key + " is doesn`t exsits");
        }else{
            node.value = value;
        }
    }

    @Override
    public int getSize(){
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

}
